Slice the fennel as finely as possible – I do this on a mandoline, but it can be done with a sharp knife if you want to protect your fingers. Save the wispy fronds to garnish.
Add the sliced fennel to a large saucepan along with the butter, and set over a medium heat. Add a generous pinch of salt and pepper and stir until everything starts to sizzle.
Reduce the heat to low and cook, stirring occasionally, until the fennel becomes extremely soft – a good 25 minutes.
Tear the ham into bits, add it to the pan and stir to coat. Pour in the cream and grate in the Parmesan. Stir until the cheese melts and you have a smooth sauce, then remove from the heat.
Bring a pan of water with a generous pinch of salt to the boil and add the pasta. Cook the pasta for 9 minutes until tender with just a little bite, then scoop out 75ml of the cooking water before draining the pasta.
Return the drained pasta to the pan with the sauce and heat until warmed through, stirring in the reserved water if it looks a little dry. Serve immediately, and don’t forget to scatter over those fennel fronds.